The two major political parties have given more than $1.3 million to candidates running for mayor and City Council since a judge overturned San Diego’s ban on such contributions in 2010.

Now council members — three of whom benefited from the new rules — must decide whether to keep that unlimited spigot of campaign cash flowing or set a limit that backers say is necessary to prevent the appearance of undue influence.

A council committee is set to consider today a cap of $20,000 on political party contributions for citywide contests — mayor and city attorney — and $10,000 for elections in council districts. If such limits had been in place during the past three years, party contributions to candidates would have totaled $198,000 instead of $1.3 million.

The proposal does not affect unlimited independent campaigns by business and labor — consistently among the biggest spenders — which are protected by the courts. Thad Kousser, an associate professor of political science at UC San Diego, recommended the party limits as a balance between preserving free speech rights and setting appropriate limits.

Kousser said limits won’t impede political parties from spending money to influence elections.

“Parties operating under such limits could still play a large role (in) San Diego politics through member communications, independent expenditures and direct contributions while not becoming conduits to circumvent other critical parts of the city’s campaign finance regime,” he said.

Kousser was one of two outside experts hired by City Attorney Jan Goldsmith to provide advice to the city.

The city currently caps individual contributions to candidates at $500; yet under the rules, that same individual can give tens of thousands to a political party, which can give that money to the candidate. Kousser cited U-T Publisher Douglas Manchester, a big supporter of former mayoral candidate Carl DeMaio, giving $65,000 to the local Republican Party, which then gave that sum to DeMaio’s campaign a short time later during last year’s race.

The debate over political party contributions began in 2010 when U.S. District Judge Irma E. Gonzalez axed some of the city’s campaign finance laws as unconstitutional in response to a lawsuit filed by the local Republican Party and others. One of the laws that was tossed out was the city’s decades-long ban on political party donations to candidates.

The city responded by adopting a $1,000 limit on party contributions, but it was struck down by Gonzalez last year. She said it was too low, but didn’t specify what threshold would be sufficient. Party contributions have been unlimited since then.

Parties used the new rule in a major way in the 2012 mayor’s race. The Republican Party gave DeMaio $829,000, while the Democratic Party gave eventual winner Bob Filner nearly $234,000.

Labor unions were actually the biggest spenders in the mayoral race, putting up $3.8 million in separate efforts in support of Filner. The city firefighters union alone spent $531,000 on Filner’s behalf, while the business-backed Lincoln Club spent $880,000 to help DeMaio.

The Ethics Commission sought input from both major parties over the past year leading up to a council decision.

One argument in favor of a contribution limit is that parties can already spend unlimited sums on communicating with members of their own party and efforts independent of the candidate.

The argument against bans or limits is that they infringe upon constitutional rights of free speech and freedom of association. Supporters of unlimited contributions say they allow for the support of robust political competition.